FCC Sulfur oxide acceptor

Abstract

An FCC sulfur oxide acceptor, its method of manufacture and use in the FCC process. The acceptor, a particulate solid containing magnesium, sodium and aluminum, the precursor of which comprises a mixture of precipitates. One precipitate is a compound of aluminum and another is a compound of magnesium. The precipitates are simultaneously precipitated from a common solution in which they have a highly limited solubility.

We claim as our invention: 
     
       1. A process for fluidized catalytic cracking of a sulfur containing hydrocarbon feedstock comprising the cycling of fluidized cracking catalyst between a cracking zone, in which said catalyst is contacted at an elevated temperature with said hydrocarbon feedstock and wherein said sulfur containing coke is deposited on said catalyst, and a regeneration zone, in which carbon and sulfur are oxidized and removed from said catalyst to form a flue gas containing sulfur oxides, said catalyst having physically admixed therewith a sulfur acceptor comprising a particulate solid other than said catalyst which contains magnesium, sodium, and aluminum, the precursor of said acceptor comprising a mixture of precipitates comprising compounds of magnesium, and aluminum, which contain compounds of sodium, said precipitates having been simultaneously precipitated at a pH of about 8.0 or above from a common solution comprising magnesium, aluminum and sodium in which said precipitates have highly limited solubility, which acceptor reacts with said sulfur oxides to form spent sulfur containing acceptor, said spent acceptor being freed from said sulfur and renewed by contacting said acceptor with a reducing gas comprising hydrogen or a hydrocarbon gas at reducing conditions, whereby said sulfur becomes dissociated from said acceptor. 
     
     
       2. The process of claim 1 wherein said catalyst comprises a crystalline aluminosilicate. 
     
     
       3. The process of claim 1 wherein said contacting of said acceptor with said hydrogen or hydrocarbon gas occurs in a reduction zone between the regeneration vessel and the reactor riser. 
     
     
       4. The process of claim 1 wherein said reducing conditions comprise a residence time of from about three seconds to about 1.0 minutes, a temperature from about 1000° F. to about 1400° F. and a pressure of from about atmospheric to about 50 psig. 
     
     
       5. The process of claim 1 wherein the sodium content in said acceptor is from about 0.10 wt.% to about 5.0 wt.% on an elemental basis, and the magnesium content is from about 10 wt.% to about 30 wt.% on an elemental basis. 
     
     
       6. The process of claim 5 wherein said acceptor comprises the oxides of sodium and magnesium in an alumina matrix. 
     
     
       7. The process of claim 6 wherein said acceptor comprises particles in the size range of from about 20 to about 150 microns.